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            Java中 VO、 PO、DO、DTO、 BO、 QO、DAO、POJO的概念 | 
        
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        <ol class="post-toc"><li class="post-toc-item post-toc-level-3"><a class="post-toc-link" href="#PO-persistant-object-持久对象"><span class="post-toc-number">1.</span> <span class="post-toc-text">PO(persistant object) 持久对象</span></a></li><li class="post-toc-item post-toc-level-3"><a class="post-toc-link" href="#DO（Domain-Object）领域对象"><span class="post-toc-number">2.</span> <span class="post-toc-text">DO（Domain Object）领域对象</span></a></li><li class="post-toc-item post-toc-level-3"><a class="post-toc-link" href="#TO-Transfer-Object-，数据传输对象"><span class="post-toc-number">3.</span> <span class="post-toc-text">TO(Transfer Object) ，数据传输对象</span></a></li><li class="post-toc-item post-toc-level-3"><a class="post-toc-link" href="#DTO（Data-Transfer-Object）数据传输对象"><span class="post-toc-number">4.</span> <span class="post-toc-text">DTO（Data Transfer Object）数据传输对象</span></a></li><li class="post-toc-item post-toc-level-3"><a class="post-toc-link" href="#VO-view-object-值对象"><span class="post-toc-number">5.</span> <span class="post-toc-text">VO(view object) 值对象</span></a></li><li class="post-toc-item post-toc-level-3"><a class="post-toc-link" href="#BO-business-object-业务对象"><span class="post-toc-number">6.</span> <span class="post-toc-text">BO(business object) 业务对象</span></a></li><li class="post-toc-item post-toc-level-3"><a class="post-toc-link" href="#POJO-plain-ordinary-java-object-简单无规则-java-对象"><span class="post-toc-number">7.</span> <span class="post-toc-text">POJO(plain ordinary java object) 简单无规则 java 对象</span></a></li><li class="post-toc-item post-toc-level-3"><a class="post-toc-link" href="#DAO-data-access-object-数据访问对象"><span class="post-toc-number">8.</span> <span class="post-toc-text">DAO(data access object) 数据访问对象</span></a></li><li class="post-toc-item post-toc-level-3"><a class="post-toc-link" href="#O-R-Mapper-对象-关系-映射"><span class="post-toc-number">9.</span> <span class="post-toc-text">O/R Mapper 对象/关系 映射</span></a></li></ol>
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                Java中 VO、 PO、DO、DTO、 BO、 QO、DAO、POJO的概念
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        <h3 id="PO-persistant-object-持久对象"><a href="#PO-persistant-object-持久对象" class="headerlink" title="PO(persistant object) 持久对象"></a>PO(persistant object) 持久对象</h3><blockquote>
<p>在 o/r 映射的时候出现的概念，如果没有 o/r 映射，没有这个概念存在了。通常对应数据模型 ( 数据库 ), 本身还有部分业务逻辑的处理。可以看成是与数据库中的表相映射的 java 对象。最简单的 PO 就是对应数据库中某个表中的一条记录，多个记录可以用 PO 的集合。 PO 中应该不包含任何对数据库的操作。</p>
</blockquote>
<h3 id="DO（Domain-Object）领域对象"><a href="#DO（Domain-Object）领域对象" class="headerlink" title="DO（Domain Object）领域对象"></a>DO（Domain Object）领域对象</h3><blockquote>
<p>就是从现实世界中抽象出来的有形或无形的业务实体。一般和数据中的表结构对应。</p>
</blockquote>
<h3 id="TO-Transfer-Object-，数据传输对象"><a href="#TO-Transfer-Object-，数据传输对象" class="headerlink" title="TO(Transfer Object) ，数据传输对象"></a>TO(Transfer Object) ，数据传输对象</h3><blockquote>
<p>在应用程序不同 tie( 关系 ) 之间传输的对象</p>
</blockquote>
<h3 id="DTO（Data-Transfer-Object）数据传输对象"><a href="#DTO（Data-Transfer-Object）数据传输对象" class="headerlink" title="DTO（Data Transfer Object）数据传输对象"></a>DTO（Data Transfer Object）数据传输对象</h3><blockquote>
<p>这个概念来源于J2EE的设计模式，原来的目的是为了EJB的分布式应用提供粗粒度的数据实体，以减少分布式调用的次数，从而提高分布式调用的性能和降低网络负载，但在这里，我泛指用于展示层与服务层之间的数据传输对象。</p>
</blockquote>
<blockquote>
<p>主要用于远程调用等需要大量传输对象的地方。<br>比如我们一张表有100个字段，那么对应的PO就有100个属性。<br>但是我们界面上只要显示10个字段，<br>客户端用WEB service来获取数据，没有必要把整个PO对象传递到客户端，<br>这时我们就可以用只有这10个属性的DTO来传递结果到客户端，这样也不会暴露服务端表结构.到达客户端以后，如果用这个对象来对应界面显示，那此时它的身份就转为VO</p>
</blockquote>
<h3 id="VO-view-object-值对象"><a href="#VO-view-object-值对象" class="headerlink" title="VO(view object) 值对象"></a>VO(view object) 值对象</h3><blockquote>
<p> 视图对象，用于展示层，它的作用是把某个指定页面（或组件）的所有数据封装起来。</p>
</blockquote>
<blockquote>
<p>通常用于业务层之间的数据传递,和PO一样也是仅仅包含数据而已.但应是抽象出的业务对象,可以和表对应,也可以不,这根据业务的需要.个人觉得同DTO(数据传输对象),在web上传递.</p>
</blockquote>
<h3 id="BO-business-object-业务对象"><a href="#BO-business-object-业务对象" class="headerlink" title="BO(business object) 业务对象"></a>BO(business object) 业务对象</h3><blockquote>
<p>从业务模型的角度看 , 见 UML 元件领域模型中的领域对象。封装业务逻辑的 java 对象 , 通过调用 DAO 方法 , 结合 PO,VO 进行业务操作。 business object: 业务对象 主要作用是把业务逻辑封装为一个对象。这个对象可以包括一个或多个其它的对象。 比如一个简历，有教育经历、工作经历、社会关系等等。 我们可以把教育经历对应一个 PO ，工作经历对应一个 PO ，社会关系对应一个 PO 。 建立一个对应简历的 BO 对象处理简历，每个 BO 包含这些 PO 。 这样处理业务逻辑时，我们就可以针对 BO 去处理。</p>
</blockquote>
<h3 id="POJO-plain-ordinary-java-object-简单无规则-java-对象"><a href="#POJO-plain-ordinary-java-object-简单无规则-java-对象" class="headerlink" title="POJO(plain ordinary java object) 简单无规则 java 对象"></a>POJO(plain ordinary java object) 简单无规则 java 对象</h3><blockquote>
<p>纯的传统意义的 java 对象。就是说在一些 Object/Relation Mapping 工具中，能够做到维护数据库表记录的 persisent object 完全是一个符合 Java Bean 规范的纯 Java 对象，没有增加别的属性和方法。我的理解就是最基本的 Java Bean ，只有属性字段及 setter 和 getter 方法！。</p>
</blockquote>
<h3 id="DAO-data-access-object-数据访问对象"><a href="#DAO-data-access-object-数据访问对象" class="headerlink" title="DAO(data access object) 数据访问对象"></a>DAO(data access object) 数据访问对象</h3><blockquote>
<p>是一个 sun 的一个标准 j2ee 设计模式， 这个模式中有个接口就是 DAO ，它负持久层的操作。为业务层提供接口。此对象用于访问数据库。通常和 PO 结合使用， DAO 中包含了各种数据库的操作方法。通过它的方法 , 结合 PO 对数据库进行相关的操作。夹在业务逻辑与数据库资源中间。配合 VO, 提供数据库的 CRUD 操作</p>
</blockquote>
<h3 id="O-R-Mapper-对象-关系-映射"><a href="#O-R-Mapper-对象-关系-映射" class="headerlink" title="O/R Mapper 对象/关系 映射"></a>O/R Mapper 对象/关系 映射</h3><blockquote>
<p>定义好所有的mapping之后,这个O/R Mapper可以帮我们做很多的工作.通过这些mappings,这个O/R Mapper可以生成所有的关于对象保存,删除,读取的SQL语句,我们不再需要写那么多行的DAL代码了.</p>
</blockquote>
<blockquote>
<p>实体Model(实体模式)</p>
</blockquote>
<blockquote>
<p>DAL(数据访问层)</p>
</blockquote>
<blockquote>
<p>IDAL(接口层)</p>
</blockquote>
<blockquote>
<p>DALFactory(类工厂)</p>
</blockquote>
<blockquote>
<p>BLL(业务逻辑层)</p>
</blockquote>
<blockquote>
<p>BOF    Business Object Framework      业务对象框架</p>
</blockquote>
<blockquote>
<p>SOA    Service Orient Architecture    面向服务的设计</p>
</blockquote>
<blockquote>
<p>EMF    Eclipse Model Framework        Eclipse建模框架</p>
</blockquote>

        
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                    <p><strong>
                         
                            This blog is andot org <a href="http://www.andot.org" target="_blank">Andot Blog</a> MIT License, 博客转载请注明出处！
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                        <br>
                        <strong>本文链接：</strong><a href="http://andot.org/2018/02/23/java-package-base-info/">http://andot.org/2018/02/23/java-package-base-info/</a>
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